1. Field of the Invention
The present invention relates to a zoom lens barrel that extends in an optical axis direction to be able to perform a zoom operation and to be retracted in a lens barrel body.
2. Description of the Related Art
Previously, in order to significantly move a lens unit in an optical axis direction to change a focal length, a zoom lens barrel has included a linear cylinder and a cam cylinder that is fitted on an outside diameter or an internal diameter of the linear cylinder to be supported so as to be rotatable around an optical axis and movable in the optical axis direction.
Japanese Patent Laid-Open No. 2005-017980 discloses a lens barrel that includes a whole unit cam groove and a whole unit pin in order to move a cam cylinder with respect to a linear cylinder. It also discloses a configuration in which a whole unit auxiliary pin cam groove and a whole unit impact cam groove are provided adjacent to the whole unit cam groove to treat them as a receiver with respect to an external pressure in an optical axis direction.
However, in the lens barrel disclosed in Japanese Patent Laid-Open No. 2005-017980, a backlash between the linear cylinder and the cam cylinder in a radial direction is easily generated at an end of a side where the whole unit cam groove is provided and an end of the opposite side in the optical axis direction. As a result, the lens unit is also tilted since the cam cylinder is tilted, and therefore an optical performance may be deteriorated.
In an optical apparatus such as a digital still camera, similarly to a digital video camera or the like, a function of taking a moving image in addition to taking a still image is obtained. In taking the moving image, a smooth zoom operation during which an image is less shaken and a high magnification are required. However, a lens barrel gets heavy when the magnification is higher, and the impact which is given by the drop is large. Therefore, the lens barrel which is strong for an external force such as an impact is necessary. Japanese Patent Laid-Open No. 2010-8802 discloses a lens barrel which improves a proof strength of a cam groove for the external force such as the impact.
However, in the lens barrel disclosed in Japanese Patent Laid-Open No. 2010-8802, although it is strong for the drop from the cam groove of a cam follower pin, a dent is formed on the cam groove when the impact is given. Therefore, when the cam follower pin passes the cam groove having the dent after the impact is given, the image shake is generated and it is difficult to perform a smooth zoom operation.